Commercial preparation of many different food and non-food products requires the use of pumping equipment suited for pumping materials which do not readily flow or are otherwise difficult to pump. For example, food products such as cheeses, lards and shortenings, ground meat, sugars, and doughs typically require the use of specialized, multi-stage pumping devices for effecting desired movement of such materials. Similarly, non-food products such as adhesives, soaps, putties and caulking compounds, and the like require the use of specialized pumping equipment if efficient handling is to be achieved.
A pumping apparatus is disclosed in U.S. Pat. No. 4,792,294. This apparatus has been found to effectively pump products which do not readily flow and for which the pump is particularly well suited. The pumping apparatus includes a pair of cooperating, counter-rotating screw augers within a housing. Each of the screw augers includes helical flights intermeshed with the flights of the other auger, and the flights are configured to provide a two-stage pumping action--namely, (1) a first, upstream, non-positive displacement pumping, and (2) a second, downstream, positive displacement pumping.
The U.S. Pat. No. 4,944,657 discloses a two-stage pump which is especially suitable for materials which can, under some conditions, undergo a change in character, consistency, or other material properties. With some products, significant changes in properties may be characterized as a loss of product integrity which is of such a nature as to render the product commercially unacceptable.
The pumping apparatus described in U.S. Pat. No. 4,944,657 provides an improved pumping apparatus for use with materials that are particularly shear sensitive so as to eliminate, or at least substantially reduce, the application of excessive shear strain on the material which might cause it to change its material characteristics.
While the above-discussed pump designs provide advantageous pumping characteristics in particular applications, there is a need to provide improved pumping apparatus for use in those applications wherein it is beneficial to minimize the pressure drop to which the material is subjected owing to changes in direction of flow from the first stage to the second stage.
It would also be desirable to provide an improved pumping apparatus which would advantageously accommodate easier assembly and disassembly.
The pumping apparatus of the present invention can be operated to effect an improved pumping process, and can be embodied in a design exhibiting the above-discussed benefits and features.